発熱(はつねつ)

はつねつ
noun
fever; generating heat
formalmedicaltechnicalhealth
1. fever, having a fever
An elevated body temperature, typically as a symptom of illness.
子供(こども)が発熱(はつねつ)した。
My child developed a fever.
発熱(はつねつ)がある場合(ばあい)は出勤(しゅっきん)しないでください。
Please don't come to work if you have a fever.
37.5度(ど)以上(いじょう)の発熱(はつねつ)は要注意(ようちゅうい)だ。
A fever of 37.5 degrees or higher requires attention.
2. heat generation, generating heat
The production of heat, used in technical and scientific contexts.
この素材(そざい)は発熱(はつねつ)する。
This material generates heat.
このヒーターは発熱(はつねつ)効率(こうりつ)が良(よ)い。
This heater has good heat generation efficiency.
化学(かがく)反応(はんのう)による発熱(はつねつ)で温度(おんど)が上(あ)がった。
The temperature rose due to heat generated by a chemical reaction.

Medical usage

発熱(はつねつ) is the medical/formal term for having a fever. It's commonly used in medical settings and official announcements.

Fever thresholds in japan

  • 37.5°C: Commonly used threshold for 'fever' in public health guidelines
  • 38°C: Generally considered moderate fever
  • 39°C+: High fever

Verb usage

  • 発熱(はつねつ)する: to develop a fever / to generate heat
  • 発熱(はつねつ)がある: to have a fever

Related words

TECHNICAL USAGE (sense 2):
In physics and engineering, 発熱(はつねつ) refers to heat generation:

  • 発熱(はつねつ)反応(はんのう): exothermic reaction
  • 発熱(はつねつ)体(たい): heating element

Related Words

Related: 熱(ねつ)
Related: 高熱(こうねつ) (high fever)
Related: 微熱(びねつ) (low-grade fever)
Related: 解熱(げねつ) (fever reduction)
Related: 解熱剤(げねつざい) (fever reducer, antipyretic)
Compare: 平熱(へいねつ) (normal body temperature)
Related: 検温(けんおん) (taking one's temperature)
general
Added 2026.1.17 17:49 · Revised 2026.9.2 12:02
06000/06297_hatsunetsu